Olefin polymerization catalysts are of great use in industry. Hence, there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties. Catalysts for olefin polymerization are often based on cyclopentadienyl transition metal compounds as catalyst precursors combined with activators, typically an alumoxane or with an activator containing a non-coordinating anion.
A typical metallocene catalyst system includes metallocene catalyst, activator, and optional support. Supported catalyst systems are used in many polymerization processes, often in slurry or gas phase polymerization processes.
Catalysts for olefin polymerization are often based on substituted metallocenes as catalyst precursors, which are activated either with the help of an alumoxane, or with an activator containing a non-coordinating anion.
For example U.S. Pat. No. 7,829,495 discloses Me2Si(fluorenyl)(3-nPr-Cp)ZrCl2 and U.S. Pat. No. 7,179,876 discloses supported (nPrCp)2HfMe2.
Further, Stadelhofer, J.; Weidlein, J.; Haaland, A. J. Organomet. Chem. 1975, 84, C1-C4 discloses preparation of potassium cyclopentadienide.
Additionally, Me2C(Cp)(Me3SiCH2-Ind)MCl2 and Me2C(Cp)(Me, Me3SiCH2-Ind)MCl2, where M is Zr or Hf have been synthesized and screened for the syndiospecific polymerization of propylene; see Leino, R, Gomez, F.; Cole, A.; Waymouth, R. Macromolecules 2001, 34, 2072-2082.
Metallocenes are often combined with other catalysts, or even other metallocenes, to attempt to modify polymer properties. See, for example, U.S. Pat. Nos. 8,088,867 and 5,516,848 (which discloses the use of two different cyclopentadienyl based transition metal compounds activated with alumoxane or non-coordinating anions). See also PCT/US2016/021748, filed Mar. 10, 2016, which discloses two metallocenes used to make ethylene copolymers.
Likewise, Me2C(Cp)(Me3SiCH2-Ind)MCl2 and Me2C(Cp)(Me, Me3SiCH2-Ind)MCl2, where M is Zr or Hf have been synthesized and screened for the syndiospecific polymerization of propylene; see Leino, R., Gomez, F.; Cole, A.; Waymouth, R. Macromolecules 2001, 34, 2072-2082.
Additional references of interest include: Hong et al. in Immobilized Me2Si(C5Me4)(N-t-Bu)TiCl2/(nBuCp)2ZrCl2 Hybrid Metallocene Catalyst System for the Production of Poly(ethylene-co-hexene) with Psuedo-bimodal Molecular Weight and Inverse Comonomer Distribution, (Polymer Engineering and Science-2007, DOI 10.1002/pen, pages 131-139, published online in Wiley InterScience (www.interscience.wiley.com) 2007 Society of Plastics Engineers); Kim, J. D. et al., J. Polym. Sci. Part A: Polym Chem., 38, 1427 (2000); Iedema, P. D. et al., Ind. Eng. Chem. Res., 43, 36 (2004); U.S. Pat. Nos. 4,701,432; 5,032,562; 5,077,255; 5,135,526; 5,183,867; 5,382,630; 5,382,631; 5,525,678; 6,069,213; 6,207,606; 6,656,866; 6,828,394; 6,964,937; 6,956,094; 6,964,937; 6,995,109; 7,041,617; 7,119,153; 7,129,302; 7,141,632; 7,172,987; 7,179,876; 7,192,902; 7,199,072; 7,199,073; 7,226,886; 7,285,608; 7,355,058; 7,385,015; 7,396,888; 7,595,364; 7,619,047; 7,662,894; 7,829,495; 7,855,253; 8,110,518; 8,138,113; 8,268,944; 8,288,487; 8,329,834; 8,378,029; 8,575,284; 8,598,061; 8,680,218; 8,785,551; 8,815,357; 8,940,842; 8,957,168; 9,079,993; 9,163,098; 9,181,370; 9,303,099; U.S. Publications 2004/259722; 2006/275571; 2007/043176; 2010/331505; 2012/0130032; 2014/0031504; 2014/0127427; 2015/299352; 2016/0032027; 2016/075803; PCT Publications WO 97/35891; WO 98/49209; WO 00/12565; WO 2001/09200; WO 02/060957; WO 2004/046214; WO 2006/080817; WO 2007/067259; WO 2007/080365; WO 2009/146167; WO 2012/006272; WO 2012/158260; WO 2014/0242314; WO 2015/123168; WO 2016/172099; PCT Application No. PCT/US2016/021757, filed Mar. 10, 2016; EP 2 374 822; EP 2 003 166; EP 0,729,387; EP 0,676,418; EP 0 705 851; KR 20150058020; KR 101132180; Sheu, S., 2006, “Enhanced bimodal PE makes the impossible possible”, http://www.tappi.org/content/06asiaplace/pdfs-english/enhanced.pdf; and Chen et al., “Modeling and Simulation of Borstar Bimodal Polyethylene Process Based on Rigorous PC-SAFT Equation of State Model”, Industrial & Engineering Chemical Research, 53, pp. 19905-19915, (2014).
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve increased activity or enhanced polymer properties, to increase conversion or comonomer incorporation, or to alter comonomer distribution.
It is also an object of the present invention to provide novel supported catalysts systems and processes for the polymerization of olefins (such as ethylene) using such catalyst systems.
It is also an object of the present invention to provide ethylene polymers having the unique properties of high stiffness, high toughness and good processability.